<!DOCTYPE html>
<html lang="en">
	<head>
		<meta charset="utf-8">
		<title></title>
		<style>
			div span,p span{
				color: green;
			}
			p span,h4 span{
				color: mediumspringgreen;
			}
		</style>
	</head>
	<body>
		<div>
		    div中的不带标签的内容
		    <span>组合选择器，注意很常用</span>
		</div>
		<p>
		    <span>p标签中的span标签</span>
		</p>
		<h4>
		    <span>h4标签中的span标签</span>
		</h4>
	</body>
</html>